1. Field of the Invention
The present invention relates to a plasma display panel, and in particular, to a design for a phosphor layer in a plasma display panel that maximizes light emission efficiency and screen brightness.
2. Description of Related Art
Generally, a plasma display panel (simply referred to hereinafter as a “PDP”) is a display device which produces a discharging gas which produces vacuum ultraviolet rays which then interacts with a phosphor layer to produce visible light to display desired images. The PDP makes it possible to provide both a high resolution display and a wide-screen display. PDPs thus are now in the spotlight for being a future generation of flat panel displays.
The PDP is largely classified into an AC type, a DC type, and a hybrid type. It is common to use an AC type triple-electrode face discharge structure. With the AC type triple-electrode face discharge structure, an address electrode, a partition wall, and a phosphor layer are formed on a rear substrate corresponding to each discharge cell, and a discharge sustain electrode with a scanning electrode and a display electrode is formed on a front substrate. Often, the front substrate is made to be optically transparent so that the visible images produced in the display can be viewed by a user through the front substrate. The discharge cell is filled with a discharge gas (a mixture of Ne and Xe).
When signals are applied to the address electrodes and the scanning electrodes when selecting the discharge cells for emitting light, and voltages of 150˜200V are applied to the scanning electrodes and the display electrodes, the discharge gas induces a plasma discharge, and vacuum ultraviolet rays with wavelengths of 147 nm, 150 nm, and 173 nm are discharged from excited Xe atoms generated during the plasma discharge. These vacuum ultraviolet rays are used to excite phosphors in the phosphor layer to generate visible rays, thereby displaying desired color images.
With the above-structured PDP, the energy efficiency of the device is reduced by numerous factors. The multiple sources of energy loss occur at each step in the conversion of an electrical voltage to the production of visible images. FIG. 6 schematically illustrates the total light emission efficiency (T) of the PDP is the sum of the energy efficiencies for each of the five steps (1) through (5). The total light emission efficiency (T) of the PDP is illustrated as the sum of (1) the circuit efficiency due to the circuit loss, (2) the discharge efficiency when the discharge power is converted into ultraviolet rays, (3) the ultraviolet utilization rate when the ultraviolet rays are converted into effective ultraviolet rays, (4) the phosphor efficiency when the effective ultraviolet rays are converted into visible rays, and (5) the visible ray utilization rate when the visible rays are converted into display light.
Many efforts have been made to minimize the energy loss at the respective steps of designing and manufacturing the PDP. All the above-identified efficiencies except for (1) the circuit efficiency are mainly affected by the internal structure and the material characteristics of the PDP. Therefore, there has been a great deal of research related to improving the internal structure and material characteristics of the PDP to improve the energy efficiencies of (2) through (5) above.
Regarding the internal structure of a PDP, the partition walls for the PDP are generally classified into either a stripe-like open type or a rectangle-like closed type. The rectangle-shaped closed type partition wall independently partitions the respective discharge cells to prevent inter-cell cross-talk, while increasing the phosphor-coated area. With both the stripe-shaped partition wall and the rectangle-shaped partition wall, the phosphor layer is formed through printing, drying, and sintering the phosphors.
Compared to the PDP with the stripe-shaped partition wall, the PDP with the rectangle-shaped partition wall results in an increased phosphor-coated area, thereby improving the phosphor efficiency (4) and the visible ray utilization rate (5). However, the phosphor layer is coated without considering the light emission efficiency (T) of the PDP, and hence, the optimized design for optimum light emission efficiency (T) is not realized.
Particularly with the PDP having a rectangular partition wall, the plasma discharge generated at each discharge cell is diffused from the space between the scanning electrode and the display electrode toward the periphery of the discharge cell in the shape of an arc. However, as the conventional phosphor layer is patterned irrespective of the diffusion shape of the plasma discharge, there are limits to improving the light emission efficiency (T) and the screen brightness.